chore: update go module, readme

readme.md

@@ -5,6 +5,7 @@
 ##### basic usage
 
 - get param
+
   ```go
   func main() {
       app := nf.New()
@@ -19,6 +20,7 @@ func main() {
   ```
 
 - parse request query
+
   ```go
   func handleQuery(c *nf.Ctx) error {
       type Req struct {
@@ -40,6 +42,7 @@ func handleQuery(c *nf.Ctx) error {
   ```
 
 - parse application/json body
+
   ```go
   func handlePost(c *nf.Ctx) error {
       type Req struct {
@@ -65,3 +68,35 @@ func handlePost(c *nf.Ctx) error {
       return c.JSON(nf.Map{"struct": req, "map": reqMap})
   }
   ```
+
+- pass local value
+
+  ```go
+  type User struct {
+      Id int
+      Username string
+  }
+
+  func main() {
+      app := nf.New()
+      app.Use(auth())
+
+      app.Get("/item/list", list)
+  }
+
+  func auth() nf.HandlerFunc {
+      return func(c *nf.Ctx) error {
+          c.Locals("user", &User{Id: 1, Username:"user"})
+          return c.Next()
+      }
+  }
+
+  func list(c *nf.Ctx) error {
+      user, ok := c.Locals("user").(*User)
+      if !ok {
+          return c.Status(401).SendString("login required")
+      }
+
+      ...
+  }
+  ```